Nuclear criticality is achieved when the fission chain reaction of fissile material such as Uranium becomes self-sustaining resulting in the release of a large amount of energy and radiation. The MNF plant utilizes low enriched uranium which has an low level of risk of an accidental criticality; however, this risk is mitigated by controlling the mass and geometry of nuclear material handled at the plant.
Uranium is handled in equipment which is geometrically shaped to physically prohibit the occurance of criticality.
This figure illustrates an ADU precipitation tank (cylindrical) used in the reconversion process. The diameter of the cylinder is designed so as to make criticality impossible.
The amount of material handled at one time is restricted so that it is physically impossible for a criticality to occur. The limit to the amount handled is established such that there is no less than a factor of 2 safety margin against criticality.